Process and apparatus for analyzing gases



Sept. 1, 1936. H. SEMRAU PROCESS AND APPARATUS FOR ANALYZING GASES Filed Sept. 10/1932 INVE TOR Patented Sept. 1, 1936 NITED ETATES PATENT OFFICE PROCESS AND APPARATUS FOR ANALYZING GASES Application September 10, 1932, Serial No. 632,542

Claims.

The invention relates to a process and apparatus for measuring, or testing, the combustible content of a gas. The gas to be analyzed, or tested, is ordinarily a gas of combustion in order to 5 determine the efl'iciency of the apparatus in which the gas is consumed, and the illustration and description are directed to the use of the apparatus in this relation, but it will be understood that the invention is not limited to use in this connection and is applicable to the measurement of gases other than gases of combustion, and to conditions wherein a gas other than the gas under analysis must be added to accomplish the analysis. The apparatus preferably operates on the principle of that shown in the patent to Max Moeller No. 1,562,243, wherein the temperature of a catalyzing wire, as affected by a gas burned adjacent thereto, is used as the determining factor in ascertaining the percentage of combustible in the gas tested, but the invention is not limited to use with this particular analyzing unit. The principal objects of the invention are:

(l) The provision of a process and apparatus in which the proportion of gas to air, as secured before analysis, is accomplished in a positive manner (instead of by means of orifices) which makes for accurate proportioning, since, with orifices (which are necessarily small), it is difficult not only to make them of the proper size, but also to keep them clean, and if the orifices are not clean their relative size as gauged by their fiow capacity is a matter of uncertainty.

(2) The provision of an apparatus and process in which the time lag (i. e. interval ensuing between the time the gas leaves the point of sampling until the analysis is indicated) is reduced to a minimum.

(3) And the provision of an apparatus which is cheap and simple as compared with apparatus now in use for the same purpose, which requires little skill to operate; which is compact; and which will give accurate results after a long period of use.

Certain embodiments of the invention are shown in the accompanying drawing, wherein:

Figure l is a diagrammatic elevation partly in section of one form of apparatus. And Fig. 2 is a similar view of a modification equipped with a fan to reduce the time lag.

The analyzing unit comprises the gas analyzing chamber I; the comparison chamber 2; the resistance elements la and 2a of platinum alloy or other material which acts as a catalytic agent in the operation of the device; and the Wheatstone bridge electric circuit, as shown, including the fixed resistances 3, 3, the galvanometer 4, the battery 5, the rheostat 6 and the ammeter 1, these elements together making up an apparatus well known in the art. The galvanometer 4, calibrated directly in terms of combustible to be analyzed, 5 measures the change. in potential across the Wheatstone bridge, caused by variations in the temperature of the platinum alloy wire la (forming one leg of the Wheatstone bridge), the temperature of which in turn is varied by burning 10 of combustible gas along its length. Any other suitable source of current may be used in place of the battery, such as the source which supplies the current for operating the motor of the fan or blower later described. The rheostat 6 gives 15 an adjustment so as to provide constant current as indicated by the ammeter l.

The apparatus which cooperates with the analyzing unit and to which the invention particularly relates (since the analyzing unit is old and 20 its place may be taken by some other form) comprises the pipe 8 for receiving the gases to be measured from a source of supply (in this case the exhaust pipe 9 of an internal combustion motor); the filter ill; the pumps II and I2 driv- 25 en from the motor I 3, and the mixing chamber 14.

The pumps are provided with the pistons l5 and [6 connected to the cranks lBa driven from mechanism in the motor casing. The motor may 30 be spring-driven or may be driven by any suitable source of power, such as electricity, depending on conditions. The cylinder of the pump II has as its inlet the pipe 8 provided at its end with the check valve l1 opening toward the cylinder. The 35 cylinder also has as its outlet the pipe [8 which leads into the mixing chamber I4, such pipe being provided with a check valve 20 opening away from the cylinder. 1

Thecylinder of the pump [2 has an inlet pipe 40 21 provided with a check valve 22 opening toward the cylinder, and an outlet pipe 23 leading into the mixing chamber and provided with a check valve 24 opening away from the cylinder. By regulating the size and speed of operation of the 45 two pumps, the proportion of gas to air supplied to the mixing chamber and the total flow may be adjusted and maintained with certainty, such as cannot be insured where orifices are depended upon to proportion the amount of gas and air. 50 The air is required in order to catalytically burn the combustible gases when they are supplied through the chamber I, as later described. The volume of diluting air as compared with the gas is preferably 10 to 12 times the value of gas, 55

ber is supplied to the chamber I through the pipe 25, such pipe being provided with an orifice 26 for reducing pulsations of fiow in combination with a diaphragm I la of yielding material, such as rubber. The chamber is supplied with an exhaus outletv 21 leading to the atmosphere.

The construction of Fig. 2 is similar to thatof Fig. 1, and similar parts are similarly numbered in the drawing, the outstanding difference being the use of the fan or blower 21 in the Fig. 2'

construction in order to speed up the fiow oil the gases from the source of supply to the analyzer and thus shorten the time'neoes'sary to secure an accurate reading from the analyzer, to which result the vent 32 contributes, as later pointed out.

Because of the excess of gas and the pressure secured in the pipe 8 on the outlet side of the' fan, it is desirable to provide for the escape of a part of the gas to the atmosphere, which object is secured by the provision of the chamber 28 in the line of flow having the outlet 29. In this apparatus, provision can also be made in the form of the vent 32 for the escape of part of the mixture of air and gas between the mixing chamber and the analyzer in case the volume supplied by the pumps is greater than that needed for analysis.

The advantages of the apparatus will be apparent from the foregoing. The use of the pumps and in some cases the fan 2'! of Fig. 2 insures a rapid fiow of gas through the pipe so that the time lag is reduced as compared with apparatus lacking the flow accelerating means. The primary purpose of the pumps is for proportioning, but if an excess volume is furnished by the pumps, their use reduces the time lag. The gas and air are proportioned positively due to the use of the pumps; as heretofore explained, so that small orifices do not have to be employed for this purpose and the readings due topartially clogged proportioning orifices is avoided. The arrangement also keeps the analyzing cell and accessory parts under a slight degree of pressure due to the compressive action of the pumps, so that trouble due to leaks in the system is avoided. The apparatus is also simplified as compared with apparatus heretofore employed commercially, and is readily portable. Other advantages will be apparent to those skilled in the art.

It will be understood that, while specific forms of apparatus are illustrated herein and a particular application of the process and apparatus to the determination of the combustible content in the exhaust from the combustion engine is shown and described, the invention is not limited in these particulars, being of wide application and possible of embodiment in a number of forms of apparatus depending on the conditions of use. Among the important fields of use is that in connection with furnaces. In this connection, the pumps may be of various forms and variously driven, the only requirement being that the operation of the pumps, by whatever means, be such as to positively and definitely regulate the proportion of diluting air to gas, as well as total fiow. The term pump is used in its broad sense and comprehends rotary pumps as well as the reciprocatig type illustrated.

What I claim is:

1. In apparatus for analyzing gas, a Wheatstone bridge electric circuit embracing an indicator and a pair of balanced resistance elements,

one of which is a catalytic agent, a chamber surrounding the resistance element which is a catalytic agent and having an outlet to the atmosphere, a mixing chamber connected with the first chamber, a pump having a suction inlet, and an outlet leading to the mixing chamber, a conduit for supplying the gas to be analyzed to the suction inlet of the pump, means located in the line of said conduit for accelerating the flow of .gas therethrough, an outlet to the atmosphere from the conduit intermediate said means. and the'pump, a second pump having a suction inlet from the atmosphere and an outlet leading to said mixing chamber, and means for operating the pumps.

stone bridge electric circuit embracing an indicator and a pair of balanced resistance elements,

- one of which is a catalytic agent, a chamber surrounding the resistance element which is a catalytic agent and having an outlet to the atmosphere, a mixing chamber connected with the first chamber, a pump having a suction inlet and an outlet leading to the mixing chamber, a conduit for supplying'the gas to be analyzed to the suction inlet of the pump, a fan located in the line of said conduit for accelerating the flow of gas therethrough, an enlargement in the conduit intermediate the fan and the pump having an outlet to the atmosphere, a second pump having a suction inlet from the atmosphere and an outlet leading to said mixing chamber, and means for operating the pumps.

3. In apparatus foranalyzing gas, a Wheatstone bridge electric circuit embracing an indicator and a pair of balanced resistance elements, one of which is a catalytic agent, a chamber surrounding the resistance element which is a catalytic agent and having an outlet to the atmosphere, a mixing chamber connected with the first chamber, a pump having a suction inlet and an outlet leading to the mixing chamber, a conduit for supplying the gas to be analyzed to the suction inlet of the pump, means located in the line of said conduitfor accelerating the flow of gas therethrough, an outlet to the atmosphere from the conduit intermediate said means and the pump, an outlet to the atmosphere intermediate the mixing chamber and the first chamber, a second pump having a suction inlet from the atmosphere and an outlet leading to said mixing chamber, and means for operating the pumps.

4. A process of analyzing the combustible content in a gas, which consists in withdrawing a portion of said gas by suction from the source of supply and feeding it under pressure through a conduit, permitting the gas thus supplied through the conduit toexpand and a part thereof to escape to the atmosphere, conducting the remainder of the gas in the conduit to a pump and supplying it by said pump in definite quantities continuously to a mixing chamber, pumping diluting air continuously into said mixing chamber in definite quantities, heating a wire of catalyzing material in a confined space electrically, conducting a portion of the mixture in said chamber to said space, permitting the escape of a portion of the mixture at a point intermediate the mixing chamber and said space, and measuring the conductivity of the wire as a gauge of I the amount of combustible content in the gas.

5. A process of analyzing the combustible content in a gas, which consists in withdrawing a portion of said gas by suction from the source of supply and feeding it under pressure through l5 2. In apparatusfor analyzing gas, a Wheatv a conduit, permitting the gas thus supplied through the conduit to expand and a part thereof to escape to the atmosphere, conducting the remainder of the gas in the conduit to a pump and supplying it by said pump in definite quantities continuously to a mixing chamber, pumping diluting air continuously into said mixing chamber in definite quantities, heating a wire of catalyzing material in a confined space electrically, conducting said mixture in said chamber to said space, and measuring the conductivity of the wire as a gauge as to the amount of combustible 5 content in the gas.

HUGO SEMRAU. 

